Line an 8 inch square pan with foil, and grease it with 1 teaspoon butter. In a saucepan combine sugar, milk, salt, and remaining butter; cook over medium heat til it boils. Boil 5 minutes, stirring constantly. Remove from the heat, and add the marshmallows, chips, nuts, and vanilla. Stir until the marshmallows and chips are melted. Spoon into pan, let it stand until set. Using foil, lift out of pan, and cut into squares. Store at room temperature. About 1 and 1/2 lbs.